San Jose Sharks center Joe Thornton (19) is defended by Detroit Red Wings defenseman Nicklas Lidstrom, of Sweden, center, during the third period in Game 2 of an NHL Western Conference semifinal Stanley Cup playoff hockey series game in San Jose, Calif.,Sunday, May 1, 2011. San Jose won 2-1.

In the final seconds, the Sharks' Joe Thornton slides into the goal next to goalie Antti Niemi. San Jose beat the Detroit Red Wings in game two of the Western Conference semifinals at HP Pavilion on Sunday.

Photo: Brant Ward, The Chronicle

In the final seconds, the Sharks' Joe Thornton slides into the goal...

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The Sharks' Joe Pavelski (right) gets into a fight with Red Wings players near their goal in the second period of game two of the Western Conference semifinals at HP Pavilion on Sunday.

Photo: Brant Ward, The Chronicle

The Sharks' Joe Pavelski (right) gets into a fight with Red Wings...

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Sharks goalie Antti Niemi manages to save a goal in the third period against the Detroit Red Wings in game two of the Western Conference semifinals at HP Pavilion on Sunday.

The Sharks' top line of Joe Thornton, Patrick Marleau and Devin Setoguchi has combined for one measly assist over the first two games against Detroit. A few years ago, if that happened in a playoff series, the sky would be falling. Lines would be shuffled, fans in a furor, offseason demolition plans in the making.

That's not a guess. It might as well be a quote from the story that ran after San Jose's first two playoff games in 2009. After combining for 222 points during the team's Presidents' Trophy regular season, the three fell flat in the first two games of the first round against the Ducks. One assist combined. Two losses, well on the way to four.

The more things stay the same, the more they change.

Lack of offense up top, it turns out, is just what is needed against the Red Wings this season. The Sharks are up 2-0 in the second-round series, with today's Game 3 at Joe Louis Arena, largely because of the defensive job Thornton's line did in the first two games against the Wings' top line, made up of superstars Pavel Datsyuk and Henrik Zetterberg and all-world goalie-screener Tomas Holmstrom.

Thornton's recalibration from a hundred-point scorer into a defensive forward was hyped throughout the season - by coaches, teammates and the media - but it's the type of shift that doesn't become real until it's tested by the best in the game. With Pittsburgh's Sidney Crosby out, Datsyuk is on the short list of players who qualify.

He put up two goals, six points and 10 takeaways in a first-round sweep of Phoenix. He has none, two and three in two games against the Sharks.

It's not as if Datsyuk is having a bad series. He looks like he's at the top of his game, a treat to watch every time he touches the puck - showing all of the vision and stick-handling ability that make him one of the greats. But Thornton's ability to control the puck on offense - limiting Datsyuk's top weapon, the takeaway - and help prevent sustained pressure going the other way has meant that Datsyuk hasn't had the puck too often.

And so it is that Thornton, who has struggled to find his identity as a playoff player, has finally become a postseason difference-maker.

Many of the Wings cited Thornton's evolution as a prime source of concern coming into the series, something that would adjust the way they played the Sharks. Defenseman Niklas Kronwall said Thornton has "become a different player," comparing him to Datsyuk.

The initial adjustments didn't work, so more are coming. According to the Detroit Free Press, Datsyuk and Zetterberg weren't playing on the same line at practice Tuesday. The Wings' thought process in putting their two offensive superstars together went something like this: The Sharks have the better secondary scoring, but if their depth gets them two goals per game, our super line can get us three.

Clearly Detroit wasn't counting on Thornton's line being quite as good at countering its top line as it has been. The two secondary-scoring goals per game have been enough for two wins.

"It's a unique situation," San Jose third-line forward Kyle Wellwood said. "Usually, the third-line guys are expected to go out and be physical against teams' top offensive players, instead of the first line.